1. Field of the Invention
This invention relates to electronic instrumentation and, more particularly, to a system for providing a visual indication of a transducer output.
2. Description of the Prior Art
Sensing devices or transducers are used to measure a large number of physical variables. Common examples of such devices are electronic thermometers, pressure gauges and strain gauges. With many of these devices the electrical output is directly proportional to the value of the physical variable being measured. Instrumentation of such "linear" devices is fairly simple since a large number of preexisting volt meters may be used. Where the output of the device does not vary linearly with the physical variable being measured, instrumentation is substantially more difficult since, in general, non-linear functions are more difficult to implement electronically. Previous methods of processing data signals from such "non-linear" transducers have concentrated on three basic methods. The first method is to utilize analog devices such as diodes to transform a non-linear response curve into a linear response curve. This method introduces significant errors into the results and it generally does not provide satisfactory results over a wide range. A second approach is to utilize hand wired digital logic circuitry in which the non-linear voltage at the output of the sensing device actuates digital logic elements when the voltage reaches previously computed set points or switch points. These devices, being hard wired, are relatively inflexible, and it is difficult to easily reprogram them when, for example, the characteristics of each of the several sensing devices used with the instrumentation are not identical. The final approach has been to utilize large scale digital computers for off line data reduction. The values of the non-linear signal are recorded with respect to time, and the recorded data is processed by the digital computer to calculate the values of the physical variable with respect to time. The basic problem with this approach is the time delay occurring between when the data is recorded and when it is processed by the digital computer.
Where more than one sensing device or transducer is to be used, it is often desirable to know the value of the physical variable measured by one device with respect to the physical variable measured by the other device. Examples of such relationships include pressure differentials, temperature ratios, etc. This is often a formidable task even for linear devices, particularly where the desired function is somewhat complex.